1. Field of the Invention
This invention pertains to heat treatment. More particularly, this invention pertains to heat treatment of aluminum or aluminum alloy parts utilizing direct infrared radiation as the heat source.
2. Description of the Prior Art
After casting an aluminum or an aluminum alloy part, it is often desirable to heat treat the part to achieve improved mechanical properties. For example, heat treatment may achieve a desired hardness to facilitate machining of the part.
A common heat treatment technique involves heating the aluminum part to about 1000.degree. F. then rapidly cooling the part. The cooling (or quenching) is followed by an aging process to stabilize the metallurgy of the part. A typical aging would involve heating the part to 300.degree. or 500.degree. F. and maintaining the part at that temperature for a period of time. By way of example, the Aerospace Material Specification AMS 2771 of the Society of Automotive Engineers issued Oct. 1, 1987, and entitled Heat Treatment of Aluminum Alloy Castings, shows heat treating aluminum alloy 356 at a temperature of 1000.degree. F. for six hours before quenching (AMS 2771, p. 10). Following quenching, AMS 2771 recommends soaking the cast part at 440.degree. F. for as much as six to twelve hours (AMS 2771, p. 11).
Recommended prior art procedures for wrought aluminum alloy parts are found in AMS 2770E as revised Jan. 1, 1989. Similarly, military specification MIL-H-6088F, effective Jul. 21, 1981, and entitled Heat Treatment of Aluminum Alloys, calls for aging 356 aluminum alloy at one to six hours at temperatures of 300.degree. to 320.degree. F. (see, MIL-H-6088F, p. 34). The ASM Committee on Heat Treatment of Aluminum Alloys suggests a treatment time of four to twelve hours at 1000.degree. F. for 356 aluminum alloy followed by an aging of three to nine hours at an aging temperature of 310.degree.-475.degree. F. (See page 685 of Metals Handbook, 9th Ed., Vol. 4, American Society for Metals (1981).
As is apparent from the foregoing, the heat treatment and aging of aluminum alloys is extremely time consuming. Furthermore, such heat treatment generally is attained in a batch process. For example, a plurality of aluminum castings are placed on a pallet or other device in a common oven and heat treated or aged as a collective group. Accordingly, there may be variations among the various castings of the batch. As a result, certain castings in the batch may not be suitably heat treated and may be subject to rejection.
It is an object of the present invention to provide a method and apparatus for reducing the required time for heat treatment of aluminum alloys. Further, it is an object of the present invention to provide a mechanism which is susceptible for use for individually heat treating a part. By individually heat treating a part, separate metallurgical records can be retained as to any given part. It is believed that in addition to having separate metallurgical records, the individual heat treatment will result in reduced scrap or waste associated with batch processing.